Air-cooled motor

ABSTRACT

An air passage extending in the axial direction of a motor shaft is formed in a plurality of places in the peripheral wall of a motor housing. An extension tube is fixed to a rear end of the motor housing to provide a space for mounting a rotary joint for connecting a coolant feed pipe to the end of a through hole in the motor shaft, and the extension tube is used as an exhaust (ventilation) passage so that the motor can be cooled with air introduced into the air passage through the tube by using a fan provided on a rear end of the extension tube.

TECHNICAL FIELD

This invention relates to the improvement of an air-cooled motorforcedly cooled down with a fan.

BACKGROUND ART

In general, an air-cooled motor is cooled down with a number of coolingfins vertically provided on the circumference of a motor housing bymaking use of natural radiation or by blowing air from a forced-aircooling fan to the cooling fins. In either case, since heat is onlyabsorbed from the motor with the medium of air contacting the surfacesof the cooling fins, satisfactory cooling effect is not expected, andbesides, it is necessary to provide a sufficient space around the motorhousing for feeding fresh air to the cooling fins at all times,resulting difficulty in arranging mechanical components close to eachother.

When an air-cooled motor is used for driving a machine tool and coolingof the air-cooled motor is carried out by blowing air from theforced-air cooling fan to the cooling fins, air having absorbed heatfrom the motor is blown against a column or a feed shaft of the machinetool, with the result that variation in the dimensions of members due tothermal expansion may lower accuracy. For this reason, it is customaryto set the blowing direction of air from the forced-air cooling fan tobe parallel with a motor shaft for preventing such a problem fromarising, and a number of machines are designed is such a manner.

However, spindle-through-coolant is often applied to the recent machinetool by directly connecting a main shaft to the motor shaft for thespeed-up of the main shaft and the improvement in power efficiency. Inthis case, as shown in FIG. 4, for instance, a motor shaft 101 has acoolant feed passage (a through hole) 100, and a coolant feed pipe 102and a pipe joint 103 are arranged on the axial rear side (that is, theside opposite to the main shaft, i.e., the right side in FIG. 4) of themotor shaft 101. On the other hand, the main shaft (not shown) islocated on the axial front side (i. e., the side of the main shaft,i.e., the left side in FIG. 4) of the motor shaft 101. Thus, aforced-air cooling fan cannot be provided on either side i.e., the axialfront side and the axial rear side of the motor shaft 101. For thisreason, a forced-air cooling fan 105 is provided in the vicinity of thecenter of a motor housing 104 in such a posture that the axial center ofa rotary shaft of the forced-air cooling fan is allowed to extendorthogonally to the axis of the motor shaft 101, as shown in FIG. 4.

In the prior art shown in FIG. 4, the center of the motor housing 104and the forced-air cooling fan 105 are covered with a hood 106, and amotor 107 is forcedly air-cooled as if the motor takes the shape of aducted fan. However, as only the center of the motor 107 is cooled,cooling efficiency of the motor is low, and if a column or a feed shaftis disposed in the course of warmed air, accuracy may be lowered.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an air-cooled motor, inwhich forced cooling of the motor can be effected with air supplied inan direction of a motor shaft, even when spindle-through coolant isused.

In order to attain the above object, an air-cooled motor according tothe present invention comprises a motor body having a motor shaft in thecenter thereof a motor housing having a plurality of air passagesextending in the direction of the axis of the motor shaft, an extensiontube having one end fixed to one end of the motor housing, and anair-cooling fan mounted on the other end of the extension tube, wherein,when the fan is rotated, outside air is first drawn into the airpassages formed in the motor housing, and then flows into the extensiontube after passing through the air passages, or outside air is firstdrawn into the extension tube and then passes through the air passagesformed in the motor housing.

Preferably, a coolant-feeding through hole is formed in the motor shaft,and one end of a coolant feed pipe extending through the extension tubeis connected to an opening end of the through hole in the motor shaftthrough a connection member.

More preferably, the connection member is arranged between the motorhousing and the fan.

More preferably, the opening end of the through hole in the motor shaftand at least a part of the connection member are covered with a closedchamber, the closed chamber is provided with a drain for the recovery ofcoolant having leaked through the connection member or a gap between theconnection member and the through hole in the motor shaft, and a drainpipe connected to the drain is arranged to lead to the outside through aperipheral wall portion of the extension tube.

According to the present invention, even an air-cooled motor, to whichspindle-through coolant is used, can be cooled down with air supplied inaxial direction of the motor shaft. Further, since there is nopossibility that air having absorbed heat from the motor is blownagainst the column or the feed shaft of the machine tool, each part ofthe machine tool can be protected from thermal expansion to maintainstable machining accuracy.

Further, since cooling of the motor is carried out with air flowingthrough the air passages formed in the peripheral wall of the motorhousing, it is not necessary to provide a wide space around the motorhousing, unlike the case of utilizing the effect of heat radiation bythe fins on the circumference of the motor housing, so that compactarrangement of machine elements around motor housing can be made.

Besides, since the connection portion between the coolant-feedingthrough hole provided in the motor shaft and the coolant feed pipe isenclosed by the closed chamber, even when the coolant leaks through theconnection portion, the coolant, together with exhaust, would not beblown against the machine tool or the like, and as a result, any problemsuch as rust on the machine tool and the abnormal condition ofelectrical equipment does not arise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view showing the structure of an air-cooledmotor according to one embodiment of the present invention;

FIG. 2 is a front view showing the air-cooled motor of FIG. 1;

FIG. 3 is a side sectional view showing a modification of the air-cooledmotor of FIG. 1; and

FIG. 4 is a schematic view showing an air-cooled motor of the prior art.

BEST MODE OF EMBODYING THE INVENTION

Hereinafter will be described one embodiment of the present inventiontogether with its modification with reference to FIGS. 1 to 3.Incidentally, FIG. 1 shows a section taken along a line A-A' in FIG. 2.

An air-cooled motor 1 as one embodiment of the present inventioncomprises a motor body 3 which is composed of a peripheral wall housing2 having a coil 14 integrally formed with a stator core, a motor shaft 6fixedly mounted with a rotor 15 composed of a rotor core and an aluminumdie casting, a head cover 16 through which the front end portion of themotor shaft 6 passes and which closes up a front end of the peripheralwall housing 2, and a bottom cover 17 through which the rear end portionof the motor shaft 6 passes and which closes up a rear end of theperipheral wall housing 2. The peripheral wall housing 2, the head cover16 and the bottom cover 17 are combined to form an entire motor housing.The motor shaft 6 is rotatably axially supported by the bearing 18mounted on the head cover 16 and the bearing 19 mounted on the bottomcover 17, respectively.

As shown in FIG. 1, in addition to the motor body 3, the air-cooledmotor 1 comprises a cylindrical extension tube 4 fixed to a rear end ofthe bottom cover 17 of the motor housing, a forced-air cooling fan 5mounted on a rear end of the extension tube 4, a closed chamber 9provided so as to cover a connection portion between a coolant-feedingthrough hole 7 formed in the motor shaft 6 of the motor body 3 and acoolant feed pipe 8, drains 10, 11 arranged in the closed chamber 9, anddrain pipes 12, 13 connected to the drains 10, 11.

As shown in FIG. 2, the peripheral wall housing 2 is comprises aprism-shaped member which is square in cross section but four corners ofthe square are chamfered and which has through hole at its center. Thethrough hole is circular in cross section and has a diameter largeenough to house the rotor 15. The peripheral wall housing 2 has first,second and third through holes as air passages 20, 21 and 22 in each ofchamfered four corners of the peripheral wall housing. These throughholes extend in parallel to the axial center of the motor shaft 6. Inaddition, the head cover 16 and the bottom cover 17 respectively fixedto the front end and the rear end of the peripheral wall housing 2 alsohave holes (not shown) in places corresponding to the air passages 20,21 and 22. These holes have the some cross section as that of the airpassages 20, 21 and 22.

The head cover 16 also has chamfered four corners similar to those ofthe peripheral wall housing 2, as shown in FIG. 2. The head cover 16 hasflanges 23 integrally formed therewith at four places corresponding tochamfered four corners of the head cover. Each flange 23 has a bolt-hole24 necessary for mounting the air-cooled motor 1 on various machines.Further, as shown in FIG. 1, in each flange 23 of the head cover 16 hasa radially outwardly opening notch 25 at a position corresponding to theplace of the bolt-hole 24. Thus, the air passages 20, 21 and 22 are notblocked with the bolts or nuts (not shown) inserted into the bolt-holes24.

The motor shaft 6 has a coolant-feeding through hole 7 formed concentricwith the axial center of the motor shaft 6. A tapered female thread forconnecting a pipe is provided on the rear end side of the through hole 7up to an opening portion of the through hole 7.

A first annular sensor element 26 is fixed to the circumference of therear end of the motor shaft 6. On the other hand, a second sensorelement 27 is fixed to the rear side surface of the bottom cover 17. Thefirst sensor element 26 and the second sensor element 27 are arrangedfacing each other leaving a predetermined space therebetween, therebyforming a position sensor to detect the rotating position of the motorshaft 6.

Further, a housing base 28 for fixing a closed chamber 9 is mounted onthe rear end surface of the bottom cover 17 through an O-ring 29 servingas a gasket. The first sensor element 26 and the second sensor element27 are arranged within a space defined by the bottom cover 17 and thehousing base 28. In the center of the housing base 28, there is a holeof a diameter enough to permit the motor shaft 6 to pierce through thehousing base, and the rear end of the motor shaft 6 is inserted throughthe hole. Further, an annular peripheral wall 30 is integrally formed inthe center of the rear side surface of the housing base 28, surroundingthe hole through which the motor shaft 6 is passed.

On the other hand, a flinger (a rotary seal member) 31 is fixed to thecircumference of the rear end of the motor shaft 6. In the center of theflinger 31, a through hole is formed for passing through the motor shaft6, while in the front side surface of the flinger, an annular recess isformed around the through hole. A part of the annular peripheral wall 30of the housing base 28 is fitted into the recess of the flinger 31.Then, when the flinger 31 is rotated in synchronism with the rotation ofthe motor shaft 6, the inner wall of the recess in the flinger 31 andthe circumferential surface of the annular peripheral wall 30 areopposed to each other with a slight space therebetween, so that a gapbetween the motor shaft 6 and the housing base 28 is made watertight.

The closed chamber 9 taking a shape a substantially cylindricalcontainer is fixed to the housing base 28. The closed chamber 9 has aflange extending from an opening end thereof outwardly in a radialdirection. The closed chamber 9 is fixed to the housing base 28 withbolts inserted into a plurality of bolt holes (not shown) formed in theflange. The closed chamber 9 fixed to the housing base is concentricwith the axial center of the motor shaft 6.

The closed chamber 9 has a flange-shaped water-proof wall 32 projectingfrom the inner surface, at its substantial axial center, inwardly in itsradial direction. A top end surface of the water-proof wall 32 isarranged to face a circumferential surface of the front end of the motorshaft 6 leaving a slight space therebetween.

Further, in the bottom of the closed chamber 9, there is a through hole,into which a fixed-side member 34 of a rotary joint 33 is fitted. Therotary joint 33 is a kind of pipe joint composed of the fixed-sidemember 34 and a rotating-side member 35, and the rotating-side member 35is freely rotatable with respect to the fixed-side member 34. Thefixed-side member 34 of the rotary joint 33 is inserted into the throughhole in the bottom of the closed chamber 9 and fixed to the bottom ofthe closed chamber 9 with a plurality of bolts. The fixed-side member 34fixed to the closed chamber is concentric with the axial center of themotor shaft 6.

On the other hand, the rotating-side member 35 of the rotary joint 33 isfixed to the motor shaft 6, and rotated together with the motor shaft 6.A tapered male thread is provided on the circumferential surface of thefront end of the rotating-side member 35, while a tapered female threadis provided on the inner surface of the rear end of the through hole 7in the motor shaft 6, so that the rotating-side member 35 is fixed tothe motor shaft 6 by fitting the tapered male thread on therotating-side member 35 into the tapered female thread on the surface ofthe through hole 7. The rotating-side member 35, fixed to the motorshaft, is rotated together with the motor shaft 6.

Since it is difficult to completely prevent the leakage of coolantthrough the connection portion between the rotating-side member 35 andthe fixed-side member 34 of the rotary joint 33, the drains 10, 11 fordraining the coolant which has leaked through these portions, to theoutside, are provided in the bottom surface of the closed chamber 9. Thecoolant having leaked through the connection portion between therotating-side member 35 and the fixed-side member 34 is allowed toremain in the closed chamber 9 with the aid of the water-proof wall 32formed on the inside of the closed chamber 9. Further, even if the levelof the coolant having leaked through the connection portion exceeds theheight of the water-proof wall 32, the linger 31 prevents the coolant inthe closed chamber 9 from intruding into the housing base 28 and alsoprevents the coolant in the closed chamber 9 from flowing outside.

The O-ring 29 is interposed in a joint portion between the housing base28 and the bottom cover 17. When the coolant having leaked through theconnection portions between the drains 10, 11 and the drain pipes 12, 13and between the rotary joint 33 and the coolant feed pipe 8 reaches thejoint portion between the housing base 28 and the bottom cover 17 by wayof the closed chamber 9 and the housing base 28 or the like, the O-ring29 prevents the coolant in the joint portion from intruding into theinside due to capillarity or the like.

The cylindrical extension tube 4 fixed to the rear end of the bottomcover 17 of the motor housing has an axial length enough to house atleast the housing base 28, the closed chamber 9 and the rotary joint 33in the extension tube. The drain pipes 12, 13 connected to the drains10, 11 provided in the bottom surface of the closed chamber 9 and thecoolant feed pipe 8 connected to the rotary joint 33 are respectivelyarranged to lead to the outside of the extension tube 4 through theholes respectively formed in a cylindrical portion of the extension tube4.

The cylindrical extension tube 4 has a flange portion 36 extending by asmall amount from the rear end of the extension tube inwardly in aradial direction. A stay 39 is fixed to the flange portion 36 with fourpieces of bolts 40. Further, an annular rectifying plate 41 is alsofixed to the flange portion 36 with these bolts 40. Then, aforced-air-cooling fan 37 and a motor 38 for driving the fan 37 forrotation are mounted on the stay 39. The fan 37 mounted on the stay 39is covered with a duct 42 fixed to the rear end of the extension tube 4.The rectifying plate 41, the fan 37 and the duct 42 constitute a turbofan.

In the air-cooled motor 1 shown in FIG. 1, air for cooling the motor isdrawn into the motor from the side of the head cover 16 and exhaustedthrough the duct 42. Otherwise, the cooling air may be drawn into themotor from the side of the duct 42 and exhausted through the head cover16 by reversing the flow direction of the cooling air. In this case, asshown in FIG. 3, the fan 37 and the rectifying plate 41 may be mountedin a posture reverse to that shown in FIG. 1.

When the fan 37 is rotated on condition that the fan 37 and therectifying plate 41 are mounted in directions as shown in FIG. 1respectively; air is drawn out of the extension tube 4, which thenproduces negative pressure, and air drawn into the air passages 20, 21and 22 through the notch 25 on the front end side of the peripheral wallhousing 2 absorbs heat from the motor 11 as the air flows through theair passages 20, 21 and 22 toward the rear of the peripheral wallhousing 2. On the other hand, when the fan 37 is rotated on conditionthat the fan 37 and the rectifying plate 41 are mounted in directions asshown in FIG. 3, respectively, outside air is drawn into the extensiontube 4 through the duct 42, and absorbs heat from the motor 1 whenflowing through the air passages 20, 21 and 22 toward the front of theperipheral wall housing 2.

As described above, according to the present invention, the cooling ofthe motor body 3 is carried out with air forcedly fed to the airpassages 20, 21 and 22 provided in the peripheral wall housing 2. Thus,an area itself of the heat radiating portion in the present invention isconsiderably small as compared with that available by a conventionalair-cooled motor having a large number of cooling is vertically providedon the circumference of the motor housing. However, according to thepresent invention, since the turbo fan is used to forcedly feed a largequantity of air into the air passages 20, 21 and 22, the air-cooledmotor in the present invention is superior in cooling performance to theprior-art air-cooled motor.

As apparent from the above description, according to the presentinvention, since it is not necessary to provide any cooling fin on thecircumference of the motor housing, the diameter of the motor itself canbe reduced, and besides, there is no possibility that warmed airresulting from absorbing heat from the motor will be blown against thecolumn or the feed shaft of the machine tool thus heating them, so thatvarious elements of the machine tool can be arranged compactly, therebyenabling the machine tool to operate with more stable machiningaccuracy.

Further, even when the leakage of coolant occurs in the connectionportion between the fixed-side member 34 and the rotating-side member 35of the rotary joint 33 or between the rotating-side member 35 and thethrough hole 7 in the motor shaft 6, the coolant having leaked throughsuch connection portions can be held in the closed chamber 9. Thus,there is no fear of having the coolant scattered together with exhaustto rust the machine tool or the electrical equipment. The coolantcollected in the closed chamber 9 can be drained outside the motor 1through the drains 10, 11 and the drain pipes 12, 13. Further, ifnecessary, a compressed air pipe 43 may be additionally connected to theinside of the closed chamber 9 to supply compressed air into the closedchamber 9 to force the remaining coolant on the bottom of the closedchamber 9 to be completely drained through the drain pipes.

What is claimed is:
 1. An air-cooled motor, comprising:a motor bodyhaving a motor shaft in a center thereof, a motor housing having aplurality of air passages extending in a direction of an axis of themotor shaft; an extension tube having a first end fixed to one end ofsaid motor housing and an air-cooling fan mounted on a second end ofsaid extension tube, said extension tube forming an internal spacebetween said motor housing and the air-cooling fan allowing at least arotary joint and piping to be arranged in the internal space, whereinwhen the air-cooling fan is rotated, outside air is first drawn into theair passages formed in said motor housing and then flows into saidextension tube after passing through the air passages, or the outsideair is first drawn into said extension tube and then passes through theair passages formed in said motor housing.
 2. An air-cooled motoraccording to claim 1, further comprising:a coolant feed pipe; acoolant-feeding through hole formed in the motor shaft; and a connectionmember, wherein a first end of the coolant feed pipe extends throughsaid extension tube and is connected to an opening end of the throughhole in said motor shaft through said connection member.
 3. Anair-cooled motor according to claim 2, wherein said connection member isarranged between said motor housing and the air-cooling fan.
 4. Anair-cooled motor according to claim 2, wherein the opening end of thethrough hole in said motor shaft and at least a part of said connectionmember are covered with a closed chamber, the closed chamber providedwith one of a drain recovering coolant having leaked through saidconnection member and a gap between said connection member and thethrough hole in said motor shaft and a drain pipe connected to the drainis arranged to lead to the outside through a peripheral wall portion ofsaid extension tube.
 5. An air-cooled motor according to claim 2,further comprising:a housing base having a through hole in a centerthereof for passing one end of said motor shaft, said housing base beingfixed to one end surface of said motor housing; and a substantiallydisc-shaped flinger fixed to a circumference of the one end of the motorshaft so that said flinger is rotated within a closed chamber as themotor shaft rotates, wherein one end surface of said housing base andone end surface of said flinger are arranged to face each other througha slight space provided therebetween to form a rotary seal memberbetween said housing base and said flinger.
 6. An air-cooled motoraccording to claim 4, wherein said connection member is a rotary jointcomposed of a rotating-side member and a fixed-side member, and therotating-side member is fitted and fixed to an end of thecoolant-feeding through hole in the motor shaft, while the fixed-sidemember extends through a wall of a closed chamber and is fixed to thewall.
 7. An air-cooled motor having a motor shaft and a housing,comprising:a plurality of air passages extending in a direction of anaxis of the motor shaft; an extension tube having a first end fixed toone end of the housing and a fan mounted on a second end of saidextension tube, said extension tube forming an internal space betweenthe housing and the fan allowing at least a rotary joint and piping tobe arranged in the internal space; wherein, when the fan is rotated,outside air is first drawn into the air passages formed in the housingand then flows into said extension tube after passing through the airpassages, or the outside air is first drawn into said extension tube andthen passes through the air passages formed in the housing.
 8. Anair-cooled motor, comprising:a motor body having a motor shaft formedwith a through hole for feeding coolant; a motor housing formed with aplurality of air passages, each extending in a direction of the motorshaft; an extension tube having a front end fixed to a rear end of saidmotor housing; a duct having a front end fixed to a rear end of saidextension tube; an air-cooling fan housed inside said duct, saidair-cooling fan drawing in outside air through the plurality of airpassages or sending outside air into the plurality of air passages; acoolant feeding pipe which goes through a peripheral wall of saidextension tube from outside to inside; and a rotary joint, arrangedinside said extension tube, said rotary joint comprising a rotating sidemember and a fixed side member, the fixed side member being connected tosaid coolant feeding pipe and the rotating side member rotating togetherwith the motor shaft, wherein coolant fed through said coolant feedingpipe is subsequently fed to the through hole to feed coolant to themotor shaft.